Four assay development studies are included in this project:(1)CD34+ cell quantitation by microvolume fluorimetry: A study comparing the biometric imaging assay, microvolume fluorimetry (MVF), to flow cytometry (FC) for quantitation of hematopoietic cells was published in August 1997 (Read et al. J Hematotherapy 1997:6: 291-301). This study demonstrated the potential utility of the MVF method as a simpler, more rapid alternative to standard FC methods for product quality control and for clinical decision-making about the timing and duration of stem cell apheresis. Plans to evaluate the final clinical CD34 assay configuration in a clinical trial did not materialize because of device malfunction and unavailability of assay kits (related to patent issues), and later to staffing issues and competing priorities, we plan to reassess these goals and implement this study in the next fiscal year. (2)Megakaryocyte progenitor cell colony (CFU-Mk) quantitation: A study evaluating the utility of CFU-Mk quantitation by the Megacult system (StemCell Technologies, Inc., Vancouver, BC, Canada) for quality assessment of G-CSF mobilized peripheral blood stem cell (PBSC) products was initiated in December 1998. Preliminary data shows that CFU-Mk content of PBSC products is highly correlated with CD34+ cell content. Ongoing studies will evaluate the relationships between these product assays and platelet engraftment after transplantation, so that the clinical utility of the assay can be assessed. Plans to complete this study were postponed until late FY 2000 because of staffing issues.(3)Quantitation of dendritic cells by flow cytometry: This study was initiated in FY 2000 in concert with our methods development for generating autologous dendritic cells for use in cancer immunotherapy. Characteristic flow cytometry features of immature dendritic cells were described in our first manuscript (see Z01 CL-02097-02 DTM).(4)Single platform flow cytometry method for quantitation of CD34+ and CD3+ cells: We plan to begin this evaluation early in FY 2001, after we purchase, install, and have staff trained on a new flow cytometer. This method will need to be compared and validated against our current dual platform method.